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  <script>
    // 题目1(选做)：const arr=['name','age','hhh','hhh','age','hhh','hhh','hhh']各出现多少次
    // 要求输出一个对象如下：{age: 2,hhh: 5,name: 1}
    const arr = ['name', 'age', 'hhh', 'hhh', 'age', 'hhh', 'hhh', 'hhh']
    let arr1 = {}
    for(key of arr){
      arr1[key]=arr1[key]? arr1[key]+1 : 1;
    }
    console.log(arr1)

    // 题目2(必做)：现在两个数组，判断在a中的元素，不在b中 const a = [1,2,3,5] const b=[1,3,5,6] 将在a不在b中的筛选出来
    // 要求：输出一个数组：[2]
    const a = [1, 2, 3, 5]
    const b = [1, 3, 5, 6]
    const c = []
  for(let i = 0 ; i < a.length ; i++){
    if(b.indexOf(a[i])===-1){
      c.push(a[i])
    }
  }
    console.log(c)
    // 题目3(必做):数组去重(可以用多种方法,至少写一种)
    // 要求：输出一个数组：[1,2,3,9]
    const arr2 = [1, 2, 3, 2, 9]
     let arr3 = []
     for(let i = 0 ; i < arr2.length ; i++){
         if(arr3.indexOf(arr2[i])===-1){
      arr3.push(arr2[i])
    }
  }
     console.log(arr3)
  </script>
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